A simple model for the time evolution of the condensation sink in the atmosphere for intermediate Knudsen numbers

Transformation of the mass flux towards the particle from the kinetic regime to the continuum regime is often described by the Fuchs-Sutugin coefficient. Kinetic regime can be obtained as a limiting case when only one term of the expansion of the Fuchs-Sutugin coefficient at small 1/Kn is considered. Here we take the two first terms into account, and get a mass flux which agrees well with the full mass flux down to Kn similar to 0.5. This procedure allows an analytical solution of the condensation equation valid for the range of intermediate Knudsen numbers to be obtained. The expansion is further applied to analytically calculate the condensation sink. The formula for the condensation sink is tested against field observations. The relative contribution of different aerosol modes to the condensation sink is discussed. Furthermore, we present a simple model describing the coupled dynamics of the condensing vapour and the condensation sink. The model gives reasonable predictions of condensation sink dynamics during the periods of the aerosol modes' growth by condensation in the atmosphere.Peer reviewe

Towards quantitative ecology : Newton’s principia revisited

Peer reviewe

35. Rakennuttajakoulutuksen tutkielmat

Julkaisu koostuu kahdestakymmenestä 35. rakennuttajakoulutuksen tutkielmasta: (1) Erno Aalto: Asuinkerrostalon suunnitteluratkaisujen optimointi kokonaisenergiatarkastelussa (2) Jukka Asikainen: Vaihtoehtoisten urakkamallien vertailu urakkapäätöstä varten - Case Ampumaurheilukeskus Napakymppi Oy (3) Pasi Henttonen: Urakkamuodon valinta energiatehokas palvelutalo (4) Kimma Kangas: Projektit kaaoksessa vai kaaoksen reunalla? Teoria rakennushankkeen riskienhallinnasta (5) Pekka Karjalainen: Sisäilmaongelmien huomioon ottaminen korjausrakentamisessa (6) Kari Kerminen: Lisä – ja muutostyöt - YSE 1998 (7) Harri Keskinen: Infrahankkeen toimintaohjeet tapaturma-, onnettomuus- ja kriisitilanteissa - Työturvallisuus, riskienhallinta (8) Jouni Koskela: Uudisrakentaminen peruskorjauksen vaihtoehtona taloyhtiöissä - Peruskorjaus ja täydennysrakentaminen (9) Jouni Lindberg: Espoon kaupungin opettaja-asunnot, omaisuusmassan straterinen kehittäminen ja toimenpide ehdotukset (10) Ismo Louhi: Kiinteistöinvestoinnin hankekuvaus ja rakennuttaminen. Suur-Seudun Osuuskauppa SSO (11) Saku Lukkala: Sisäilmaongelmien haltuunotto - Asiakasprojekteihin liittyvä toimintaohjeisto (12) Priit Nukka: Turvallisuuskoordinaattorin tehtävät Tampereen työväenteatterin toisen vaiheen laajennuskohteessa (13) Anja Rinta-Jaskari: Jaetun urakan ja projektinjohtourakan soveltuvuuden tarkastelu korjausrakennuskohteessa (14) Marita Rovamo: Puhtaudenhallinta rakennushankkeessa (15) Kyösti Schwartz: LEAN-ajattelun periaatteiden hyödyntäminen hankkeen projektinjohtopalvelumallissa rakennuskonsultin tehtävien osalta (16) Tapio Siirto: Katujen kuntoluokkakartat (17) Katriina Silvan: Rakennuttajan turvallisuuskoordinaattorin tehtävät käytännössä - Perustajaurakointi, asuinrakentaminen, uudisrakentaminen (18) Heikki Sopanen: Kaatron koulu rakennuttaminen - Peruskorjauksesta uudisrakennukseksi (19) Kari Visunen: Rakennuttajakonsultin suunnittelun ohjaus teollisuusprojektissa (20) Nina Väistö: Strategialähtöisen toimitila-analyysin hyödyistä kiinteistökehittämisess

Formation and growth of sub-3-nm aerosol particles in experimental chambers

Atmospheric new particle formation (NPF), which is observed in many environments globally, is an important source of boundary-layer aerosol particles and cloud condensation nuclei, which affect both the climate and human health. To better understand the mechanisms behind NPF, chamber experiments can be used to simulate this phenomenon under well-controlled conditions. Recent advancements in instrumentation have made it possible to directly detect the first steps of NPF of molecular clusters (similar to 1-2 nm in diameter) and to calculate quantities such as the formation and growth rates of these clusters. Whereas previous studies reported particle formation rates as the flux of particles across a specified particle diameter or calculated them from measurements of larger particle sizes, this protocol outlines methods to directly quantify particle dynamics for cluster sizes. Here, we describe the instrumentation and analysis methods needed to quantify particle dynamics during NPF of sub-3-nm aerosol particles in chamber experiments. The methods described in this protocol can be used to make results from different chamber experiments comparable. The experimental setup, collection and post-processing of the data, and thus completion of this protocol, take from months up to years, depending on the chamber facility, experimental plan and level of expertise. Use of this protocol requires engineering capabilities and expertise in data analysis.Peer reviewe

Sensitivity of aerosol concentrations and cloud properties to nucleation and secondary organic distribution in ECHAM5-HAM global circulation model

The global aerosol-climate model ECHAM5-HAM was modified to improve the representation of new particle formation in the boundary layer. Activation-type nucleation mechanism was introduced to produce observed nucleation rates in the lower troposphere. A simple and computationally efficient model for biogenic secondary organic aerosol (BSOA) formation was implemented. Here we study the sensitivity of the aerosol and cloud droplet number concentrations (CDNC) to these additions. Activation-type nucleation significantly increases aerosol number concentrations in the boundary layer. Increased particle number concentrations have a significant effect also on cloud droplet number concentrations and therefore on cloud properties. We performed calculations with activation nucleation coefficient values of 2 x 10(-7) s(-1), 2 x 10(-6) s(-1) and 2 x 10(-5) s(-1) to evaluate the sensitivity to this parameter. For BSOA we have used yields of 0.025, 0.07 and 0.15 to estimate the amount of monoterpene oxidation products available for condensation. The hybrid BSOA formation scheme induces large regional changes to size distribution of organic carbon, and therefore affects particle optical properties and cloud droplet number concentrations locally. Although activation-type nucleation improves modeled aerosol number concentrations in the boundary layer, the use of a global activation coefficient generally leads to overestimation of aerosol number. Overestimation can also arise from underestimation of primary emissions.The global aerosol-climate model ECHAM5-HAM was modified to improve the representation of new particle formation in the boundary layer. Activation-type nucleation mechanism was introduced to produce observed nucleation rates in the lower troposphere. A simple and computationally efficient model for biogenic secondary organic aerosol (BSOA) formation was implemented. Here we study the sensitivity of the aerosol and cloud droplet number concentrations (CDNC) to these additions. Activation-type nucleation significantly increases aerosol number concentrations in the boundary layer. Increased particle number concentrations have a significant effect also on cloud droplet number concentrations and therefore on cloud properties. We performed calculations with activation nucleation coefficient values of 2 x 10(-7) s(-1), 2 x 10(-6) s(-1) and 2 x 10(-5) s(-1) to evaluate the sensitivity to this parameter. For BSOA we have used yields of 0.025, 0.07 and 0.15 to estimate the amount of monoterpene oxidation products available for condensation. The hybrid BSOA formation scheme induces large regional changes to size distribution of organic carbon, and therefore affects particle optical properties and cloud droplet number concentrations locally. Although activation-type nucleation improves modeled aerosol number concentrations in the boundary layer, the use of a global activation coefficient generally leads to overestimation of aerosol number. Overestimation can also arise from underestimation of primary emissions.The global aerosol-climate model ECHAM5-HAM was modified to improve the representation of new particle formation in the boundary layer. Activation-type nucleation mechanism was introduced to produce observed nucleation rates in the lower troposphere. A simple and computationally efficient model for biogenic secondary organic aerosol (BSOA) formation was implemented. Here we study the sensitivity of the aerosol and cloud droplet number concentrations (CDNC) to these additions. Activation-type nucleation significantly increases aerosol number concentrations in the boundary layer. Increased particle number concentrations have a significant effect also on cloud droplet number concentrations and therefore on cloud properties. We performed calculations with activation nucleation coefficient values of 2 x 10(-7) s(-1), 2 x 10(-6) s(-1) and 2 x 10(-5) s(-1) to evaluate the sensitivity to this parameter. For BSOA we have used yields of 0.025, 0.07 and 0.15 to estimate the amount of monoterpene oxidation products available for condensation. The hybrid BSOA formation scheme induces large regional changes to size distribution of organic carbon, and therefore affects particle optical properties and cloud droplet number concentrations locally. Although activation-type nucleation improves modeled aerosol number concentrations in the boundary layer, the use of a global activation coefficient generally leads to overestimation of aerosol number. Overestimation can also arise from underestimation of primary emissions.Peer reviewe

Towards a concentration closure of sub-6 nm aerosol particles and sub-3 nm atmospheric clusters

Atmospheric clusters play a key role in atmospheric new particle formation and they are a sensitive indicator for atmospheric chemistry. Both the formation and loss of atmospheric clusters include a complex set of interlinked physical and chemical processes, and therefore their dynamics is highly non-linear. Here we derive a set of simple equations to estimate the atmospheric cluster concentrations in size ranges of 1.5–2 nm and 2–3 nm as well as 3–6 nm aerosol particles. We compared the estimated concentrations with measured ones both in a boreal forest site (the SMEAR II station in Hyytiälä, Finland) and in an urban site (the AHL/BUCT station in Beijing, China). We made this comparison first for 3–6 nm particles, since in this size range observations are more reliable than at smaller sizes, and then repeated it for the 2–3 nm size range. Finally, we estimated cluster concentrations in the 1.5–2 nm size range. Our main finding is that the present observations are able to detect a major fraction of existing atmospheric clusters.Atmospheric clusters play a key role in atmospheric new particle formation and they are a sensitive indicator for atmospheric chemistry. Both the formation and loss of atmospheric clusters include a complex set of interlinked physical and chemical processes, and therefore their dynamics is highly non-linear. Here we derive a set of simple equations to estimate the atmospheric cluster concentrations in size ranges of 1.5–2 nm and 2–3 nm as well as 3–6 nm aerosol particles. We compared the estimated concentrations with measured ones both in a boreal forest site (the SMEAR II station in Hyytiälä, Finland) and in an urban site (the AHL/BUCT station in Beijing, China). We made this comparison first for 3–6 nm particles, since in this size range observations are more reliable than at smaller sizes, and then repeated it for the 2–3 nm size range. Finally, we estimated cluster concentrations in the 1.5–2 nm size range. Our main finding is that the present observations are able to detect a major fraction of existing atmospheric clusters.Peer reviewe

Finnish Centre of Excellence in Physics, Chemistry, Biology and Meteorology of Atmospheric Composition and Climate Change : summary and outlook

Peer reviewe

The Center of Excellence in Atmospheric Science (2002–2019) — from molecular and biological processes to the global climate

The study of atmospheric processes related to climate requires a multidisciplinary approach, encompassing physics, chemistry, meteorology, forest science, and environmental science. The Academy of Finland Centre of Excellence in atmospheric sciences (CoE ATM) responded to that need for 18 years and produced extensive research and eloquent results, which are summarized in this review. The work in the CoE ATM enhanced our understanding in biogeochemical cycles, ecosystem processes, dynamics of aerosols, ions and neutral clusters in the lower atmosphere, and cloud formation and their interactions and feedbacks. The CoE ATM combined continuous and comprehensive long-term in-situ observations in various environments, ecosystems and platforms, ground- and satellitebased remote sensing, targeted laboratory and field experiments, and advanced multi-scale modeling. This has enabled improved conceptual understanding and quantifications across relevant spatial and temporal scales. Overall, the CoE ATM served as a platform for the multidisciplinary research community to explore the interactions between the biosphere and atmosphere under a common and adaptive framework